The overall objectives of the proposed research are: 1) to characterize alterations in human prostate carcinoma at the subcellular level utilizing electron microscopy (TEM, SEM) and immunocytochemistry to further improve prognostication based on Mostofi's histopathologic grading system, 2) to study differentiation of untreated, and tumor potential of carcinogen-treated, cultured explants via xeno-transplantation into nude (athymic) mice, 3) to examine modulation of carcinogenesis in vitro by vitamin A analogs, and steroid hormones (testosterone, dihydrotestosterone, and estradiol), 4) to investigate DNA binding and production of metabolites by radiolabeled dimethyl benzanthracene and effects of steroid hormones on aryl hydrocarbon hydroxylase induction, and 5) to determine the distributional patterns of hormone binding sites in vitro and in retrospective, histopathologic material using radio-autographic detection of tritium-labeled steroids.